JPH09264724A - Method for inpsecting package of semiconductor device and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a warpage of a package of a semiconductor device. SOLUTION: When a warpage of a package 12 of a semiconductor device 10 is detected, at first, a plurality of points are positioned on a common face of the package 12 by means of an imaging device 19. Next, a distance from the face of the package 12 to a reference 20 is measured by means of the imaging device 19 and values of the plurality of the measured distances are compared with each other in order to detect the warpage of the package 12.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to semiconductor devices, and more particularly to improved apparatus and methods for detecting semiconductor device package warpage.

[0002]

BACKGROUND OF THE INVENTION When testing and loading semiconductor devices, it is necessary that the device leads be properly positioned and that the ends of the leads be on a common plane. This is especially true for surface mount devices. The leads of the semiconductor device may be bent laterally, outwards, inwards or downwards, causing the ends of the leads to move away from the common plane of the ends of other leads. In some examples, one or more leads may be taller than other leads.

Further, the warpage of the semiconductor device package causes a problem when the device is mounted on the circuit board. Due to the warp of the package body, the lead wires of the device are not installed on the common surface. This results in the components not being properly loaded onto the circuit board, especially when automatic placement equipment is used. Further, there is currently no known inspection device for detecting the warp of the package during or immediately after the completion of the element in the manufacturing facility. Warpage of the package is therefore typically not found until the device is placed on a circuit board or until board level electrical testing. The lack of real-time detection of warpage in this package prevents corrective action for this or the issue of warpage.

Conventional devices for inspecting the coplanarity of leads on semiconductor devices have been developed. Two such devices are described in US Pat. No. 5,402,505 and US Pat. No. 5,414,458 assigned to the assignee of Texas Instruments. However, there is no known device for detecting the warp of the package body. Therefore, although there is an apparatus for inspecting the lead wire, there is a possibility that a warp may occur in the package, which deteriorates the usefulness of the device.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and apparatus for detecting warpage in a semiconductor device package.

[0006]

One aspect of the present invention provides a method for detecting warpage in a package of a semiconductor device having a plurality of leads with an imaging device. The method includes positioning a plurality of points on a common surface of the package with an imaging device. The method also includes measuring the distance from the plane of the package to the reference with the imaging device and comparing the plurality of distance measurements with each other to detect package warpage.

Another aspect of the present invention provides an apparatus for detecting warpage in a package of a semiconductor device having a plurality of leads. The apparatus includes a camera that captures the image of the device and a viewing device that positions multiple points in the common plane of the package from the image of the device. The viewing device can measure the distance from the surface of the package to the reference. The apparatus also includes a processor that compares a plurality of distance measurements with each other to detect package bow.

Yet another aspect of the present invention provides a method for detecting a warp in a package of a semiconductor device having a plurality of leads by an imaging device. The method involves illuminating the package and positioning a plurality of points on a common plane along the bottom of the package with an imaging device.
The method also includes measuring the distance from the fiducial to at least three points on the surface of the package with an imaging device, the three points being the center of the package and the two side edges. The method involves calibrating the distance observed by the imager to a linear distance and comparing the distance measurements with each other to detect warpage in the package.

The device and method of the present invention provide several technical advantages. One advantage of the device and method of the present invention is that it detects warpage of the package body. This can prevent unacceptable devices from being shipped. Further, the present invention provides the technical advantage of providing immediate feedback to the package manufacturing process for problem correction operations by detecting package warpage as part of or closely related to the manufacturing process.
On the other hand, package warpage was previously detected only when the device was placed on the circuit board after a few weeks or months, but the device of the present invention does not detect package warpage within minutes or hours of forming the package. To detect the warp of. This makes it much easier to recognize variations in the package manufacturing process that may have caused package warpage.

Another technical advantage of the present invention is that it provides more real-time feedback to the manufacturing process so that problems in the manufacturing process can be more quickly identified. This reduces waste associated with erroneous manufacturing processes and also improves manufacturing process productivity.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention is illustrated in the drawings, wherein like reference numbers indicate like and corresponding parts throughout the various drawings. FIG. 1 illustrates the optical paths and components of a package inspection system incorporating the inventive concept of the present invention. The semiconductor device 10 of FIG. 1 is a package 1
Located on a rotatable platform or base 16 in front of the lighting device 18 having two and a plurality of leads 14. Package 12 is typically formed from a plastic mold or other suitable material.

FIG. 1 shows a video device 19 for detecting warpage of the package 12 of the element 10. The device 19 may be implemented in a Texas Instruments AT4070 lead inspection device.

As shown in FIG. 1, the real time reference unit 2
The 0 is placed close to the element 10. The image device 19 allows the device 10, the base 16 and the real-time reference device 2
An image of 0 is provided to the camera 21 as follows. Images of the illuminated element 10, base 16 and real-time reference 20 are formed along a through hole 22 and, via mirror assembly 24, these images are reflected along a passageway 26 toward a mirror 28. Mirror 28 reflects the image at an angle of 45 degrees and follows path 30 to mirror / beam splitter 32 where the image is split into two images. The first image is reflected and passed through the passage 36 to the reflector 3
Go to 8. The first reflection image returns along path 40,
Mirror / beam splitter 32 along path 42 towards lens assembly 44 and camera 21.

A second image of semiconductor device 10, base 16 and real time reference 20 is also passed through mirror / beam splitter 32 from passage 46 to reflector 48 and inverted along passage 50 to mirror / beam splitter 32. And then reflects and travels along path 52 to lens assembly 44 where they converge on camera 21. During the splitting of the images at the mirror / beam splitter 32, the two image sets are separated so that the images 54 and 56 are vertically and horizontally spaced and horizontally offset from the camera 21 with respect to each other. Please note that. On the other hand, the camera 21 is connected to the computer-controlled observation device 57. Device 57 is camera 2
Data from one view image may be received and the data may be processed in processor 55. Camera 2
1, the device 57 and the processor 55 may be incorporated in a single device without departing from the inventive concept.

For example, the camera 21 is a highly reliable Kodak "MegaPlus"("MegaP" excluding the shutter.
a full frame high resolution charge-coupled device (CCD) camera, such as the "lus"). The need for an electromechanical shutter for the camera 21 can be eliminated by a strobe illuminator 48 at a speed compatible with the computer controlled viewing device 57. The camera 21 has a known scanning and frame rate, and the irradiation device 18 can provide a stable image to the observation device 57 by synchronizing with the scanning and frame speed of the camera.

FIG. 2 is a top view of the optical passages represented by passages 22 and 26 and mirror assembly 24 of FIG. The element 10, the base 16 and the real-time reference 20 are located in front of the illumination device 18, and the image of the element 10, the base 16 and the real-time reference 20 is directed along the passageway 22 to the mirror assembly 24. Mirror assembly 24 includes two mirrors 58 and 60 that are vertically oriented and are positioned at a 90 degree angle to each other. The images of the element 10, the base 16 and the real-time reference 20 hit the mirror 58, are reflected by the mirror 60,
Head towards the mirror 28. The mirror 28 is located at 45 degrees from the horizontal as shown in FIG.

FIG. 3 shows the semiconductor device 10, the base 16 and the real time reference 20. When detecting the warpage of the package 12 of the element 10, the base 16 is rotated so that each of the four sides of the element 12 is exposed to the camera 21. The base 16 is rotatable, and each of the four sides 16a, 16b, 16c and 16d is rotated in the direction of the camera image path such that each side of the package 12 is positioned toward the camera 21.

The element 10 is arranged on the base 16 in the opposite direction to the mounting position, for example, upside down. The package 12 of the device 10 includes a top surface 64 and a bottom surface 66. Also shown in FIG. 3 are package reference points A, B and C along each side edge of body 12. Reference point A,
B and C recognize the position of the bottom surface 66 of the package body 12, and are used for determining the coplanarity of the package body 12, that is, detecting the warp. Note that the present invention is not limited to the use of the number of reference points shown in FIG. Although the three reference points are preferable scores for detecting the warp of the package 12, these scores can be changed without changing the concept of the present invention.

FIG. 4 shows camera images of device 10, base 16 and real-time reference 20. The invention is particularly thin-quad-flat-p.
ack: TQFP) This is advantageous for detecting warpage of the element. Since the leads are on all four sides of the package,
These elements are known as quad flat packs. The semiconductor device 10 is shown as a TQFP device in the drawing. T
QFP devices typically have a package body depth 68 of 1.5 mm or less. Typical dimensions for the depth 68 of the package 12 would be 1 mm or 40 mils. Further, the height 70 of the lead wire 14 from the bottom 66 of the package 12 is typically about 2 mils.

The real-time reference 20 provides a reference for calibrating the pixels in the camera 21 and computer-controlled viewing device 57 to linear measurements of distance, eg, mils. Knowing the dimensions 72 and 74 of the aperture 75 of the real-time reference 20, the number of picture elements across the aperture measured by the camera 21 can be correlated to a linear measurement of mils.
The correlation of the pixel with the mils is achieved by the detection of the white-black transition of the aperture 75 for the illuminator 18.

To detect warpage of the body 12 of the element 10, a measurement is made by the camera 21 on the bottom surface 66 of the body 12. This can be accomplished in two ways. First,
Real time reference 20 bottom end 76 and package body 1
The distance between the bottom surfaces 66 of the two is the reference points A and B of the package 12.
And C. These measurements are represented in FIG. 4 as distances 78, 80 and 82, respectively. Package 1
The warp of 2 is then determined by comparing these distances. (See Figure 5 to further illustrate this method of detecting package warpage.)

As an alternative, the warpage of the package 12 can be determined by first determining the lead bearing surface 71 for the lead 14 of the device 10. When the lead wire seating surface is determined, the distances between the lead wire seating surface 71 and the reference points A, B and C on the bottom surface 66 of the package 12 are measured. These measurements are represented by the reference numbers 86, 88 and 90 in FIG. These measurements are then compared to each other to determine if the body 12 is warped. (Measured value 86,
88 and 90 are shown offset from measurements 78, 80 and 82 for purposes of illustration only. See also FIG. 6, which further illustrates this method of detecting package bow. )

The warp of the package 12 using any one of the above methods is expressed by the following equation.

[Equation 1] Here, A = distance 78 or 86 at the reference point A B = distance 80 or 88 at the reference point B C = distance 82 or 90 at the reference point C

The warp along each side of the package 12 is
It is measured by rotating the base 16 to expose each side of the element 10 to the camera 21 and repeating the above measurements. In FIG. 4, the side surface 16a is visible and the element 10
And seeing the base 16. The example of FIG. 4 shows the warpage of the package 12 near point C. By comparing the measured values of the reference points A, B and C with the riltime reference device 20 or the lead bearing surface 71, this warp can be automatically detected by using the present device.

FIG. 5 shows an exemplary flow chart for executing the semiconductor device package inspection method of the present invention. The process begins by forming a package for 92, eg, a number of semiconductor devices, and placing a first device on the base 16. Next, at step 94, the video picture element is
Correlated to linear distance measurements in s or millimeters. In step 94, the camera 21 and the computer controlled viewing device 57 achieve calibration with the known aperture spacings 72 and 74 of the real time reference 20.

In step 96a, the real time reference 2
The bottom surface 76 of the zero is positioned using the white-black transition of the reference 20 associated with the illuminator 48. The bottom surface 66 of the package 12 is the white of the package related to the irradiation device 18.
Positioning is performed in step 100 by detecting a black transition. At step 102, a package reference point, eg, points A, B, and C along the first side edge, is recognized.

In step 104a, the distance between the bottom surface 66 of the package 12 and the bottom surface 76 of the real-time reference 20 at the package reference point is created. Step 106a
At, a question is asked as to whether all measurements along all side edges of the package 12 have been completed. If there are additional points about the measurement, the flow is step 1
Returning to 04, the distance between the real time reference 20 and the additional reference point is measured.

Once the distances to all reference points for one side have been measured, flow proceeds to step 108 where the bow along the side is calculated according to the above equation.
Returning to FIG. 5, if warpage of the other side of the package 12 should be observed, flow proceeds to step 112, where the device is rotated and steps 98 and 108 are performed.
Is repeated.

Once the bow of all sides of a given element has been measured, the flow then proceeds to step 113, where
Questions are asked as to whether more elements are present in many elements. If another element is present, flow proceeds to step 114, where the next element is loaded into base 16 and steps 96-112 are repeated. Once the bow in all the devices in a given lot has been measured, the flow proceeds to step 116 where the measured bow for each device is compared to a predetermined tolerance. For example, for 1mm or 40mils thick packages,
2 mils coplanarity is desirable. This is 2 on the package above or below other points
It means that there are no more points than mils. Step 10
The warpage of each package calculated at 8 is compared to this tolerance at step 116 and unacceptable components are identified and removed from the lot. Next, step 1
At 18, the analysis results of step 116 may be analyzed for proper corrective action in the package manufacturing process that caused the package to warp. Further, at step 116, these warped devices may be classified and the data from the package test recorded for use in statistical process control (SPC) analysis.

FIG. 6 provides another exemplary flow chart for device package inspection. In FIG. 5, the warp of the package is detected by measuring the distance between the real-time reference device 20 and the package bottom surface 66, but the method of FIG. 6 measures the distance between the package bottom surface 66 and the lead wire seat surface 71. Detects package warpage.

The method shown in FIG. 6 is very similar to the method shown in FIG. One notable difference is step 96a in FIG.
Is replaced in step 96b, which requires positioning of the leads 14 of the device 10. This is accomplished using the lead white-black transition associated with the illuminator 18. The method of FIG. 6 also includes determining the lead bearing surface in step 98. This is surface 71
It can be calculated by using the top three points. Further, the flow of FIG. 6 includes step 104b instead of 104a for measuring the distance between the package bottom surface 66 and the lead wire seat surface 71 at each package reference point.
The measured values between the lead wire seating surface 71 and the package bottom surface 66 are then used to detect warpage of the package body. The other flow of FIG. 6 is similar to the flow of FIG. Also, FIGS.
It should be noted that the above method is exemplary only and does not limit the scope of the invention. The steps of FIGS. 5 and 6 may be modified or combined in order without departing from the inventive concept of the invention.

The apparatus and method of the present invention provide the technical advantage of detecting warpage of the device package which affects the placement of the device on the circuit board. Warpage detection is done in real time during the manufacturing process so that unacceptable elements are detected and excluded from the deliverable lot. Further, since the apparatus of the present invention detects the warp in real time, it is easy to recognize the cause of the warp, thereby minimizing the waste caused by an erroneous process and improving the productivity of the manufacturing process of the package.

While this invention has been described in detail, various changes and substitutions can be made without departing from the spirit and scope of the invention as set forth in the appended claims.

With respect to the above description, the following items will be disclosed. (1) A method for detecting a warp of a package of a semiconductor device having a plurality of lead wires by an image device, wherein a plurality of points are positioned on a common surface of the package by the image device, and the image device detects from the surface of the package. A method as described above comprising the steps of measuring a distance to a reference and comparing a plurality of distance measurements with each other to detect package warpage. (2) The method according to item 1, further comprising the step of calibrating the distance observed by the image device into a linear distance. (3) The method according to item 1, further comprising the step of calibrating the picture elements observed by the video device into a linear distance.

(4) The method of claim 1 wherein the measuring step further comprises detecting the package and reference black-white transitions against a white background with an imaging device. (5) The method according to item 1, further comprising the step of irradiating the package. (6) The method of claim 1 further comprising the step of positioning the seat surface for the lead wire of the device with the imaging device and using the seat surface as a reference for the measuring step. (7) The method according to item 1, wherein the reference is a real-time reference placed close to the package. (8) The package surface has a bottom surface of the package, and the measuring step further comprises measuring the distance from the reference to at least three points on the package surface, the three points being the center of the package side and 2 The method of claim 1 wherein the method is proximate to one end.

(9) The method of claim 1 wherein the measuring step further comprises measuring the distance from the package surface to the reference along each side of the package. (10) A device for detecting warpage of a package of a semiconductor device having a plurality of lead wires, which is a camera for capturing an image of the device, an image device for locating a plurality of points on a common surface of the package from the image of the device, and an image The apparatus further comprising a processor operable to measure a distance from the package surface to the reference, and to compare the plurality of distance measurements with each other to detect package warpage.

(11) The device according to the tenth item, wherein the video device operates so as to calibrate the distance observed by the camera to a linear distance. (12) A first operation in which the video device further operates to detect a package and reference black-white transition on a white background.
The apparatus according to item 0. (13) The apparatus according to item 10, further comprising an irradiation device that irradiates the package. (14) An apparatus according to claim 10 which is operable to position the lead surface of the element from the imager or the image and to use the lead seat surface as a reference.

(15) The apparatus according to the tenth item, wherein the reference is a real-time reference placed close to the package. (16) The package surface has a bottom surface of the package, and the imaging device measures distances from the reference to at least three points on the package surface, the three points being close to the center of the package side surface and two edges. Item 10. The apparatus according to item 10 above. (17) The apparatus according to claim 10, further comprising a rotation base that rotates the package so that each side of the package is exposed to the camera. (18) A method for detecting warpage of a package of a semiconductor device having a plurality of lead wires by an image device,
Illuminating the package, positioning a plurality of points on a common surface along the bottom surface of the package with an imaging device, measuring the distance from the reference to at least three points on the package surface with the imaging device, A point having the center of the package and two side edges, calibrating the distance observed by the imager to a linear distance,
And the method of comparing a plurality of distance measurements with one another to detect package warpage.

(19) The method according to item 18, further comprising the step of calibrating the picture elements observed with a video device into a linear distance. (20) The method according to claim 18, further comprising the steps of positioning a seat surface for a lead wire of the device by an imaging device, and using the seat surface as a reference for the measuring step. (21) A package (1) of a semiconductor device (10) having a plurality of lead wires (14) by an imaging device (19).
A method for detecting the warp of 2) is provided. The method involves positioning a plurality of points (A, B and C) on a common surface of the package with an imaging device (19). In addition, this method uses a video device (19) to
Distance from (0) to the reference (20 and 71) ((78,
80, 82) or (86, 88, 90)),
And including comparing the plurality of distance measurements with each other to detect warpage of the package (12).

[Brief description of drawings]

FIG. 1 shows a folded optical path and associated components that can be used in an inspection device to implement the concepts of the present invention.

2 is a top view of a portion of the optical passage of FIG. 1. FIG.

FIG. 3 is a perspective view of a real time fiducial, a loading base and a semiconductor device.

FIG. 4 is a view showing a real-time reference device, a loading base, and a semiconductor element as viewed from an observation device.

FIG. 5 is an exemplary flow chart diagram illustrating steps of a method for detecting package bow according to the present invention.

FIG. 6 is another flow chart diagram illustrating the steps of a method for detecting package bow according to the present invention.

[Explanation of symbols]

 10 semiconductor element 12 package 14 lead wire 19 image device 20, 71 reference 78, 80, 82, 86, 88, 90 distance

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[Procedure amendment]

[Submission date] March 7, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

[Figure 5]

[Procedure 3]

[Document name to be amended] Drawing

[Correction target item name] Fig. 6

[Correction method] Change

[Correction contents]

FIG. 6

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Clyde M. Guest United States Plano, Texas, Port Side Lane 3256

Claims (2)

[Claims] 1. A method for detecting a warp of a package of a semiconductor device having a plurality of lead wires by a video device, wherein a plurality of points are positioned on a common surface of the package by the video device, and The foregoing method comprising the step of measuring the distance from the surface to the reference and comparing the plurality of distance measurements with each other to detect the warpage of the package. 2. A device for detecting a warp of a package of a semiconductor device having a plurality of lead wires, which is a camera for capturing an image of the device, and an image device for positioning a plurality of points on a common surface of the package from the image of the device. Wherein the imaging device is further operative to measure the distance from the package surface to the reference, and said device having a processor for comparing the plurality of distance measurements with each other to detect warpage of the package.